In a normal engine in which a piston and a crankshaft disposed on a cylinder axis are connected via a connecting rod, since the direction of secondary vibration of the engine is parallel to the direction of the cylinder axis, a pair of balancer shafts of a secondary balancer system are generally arranged symmetrically on opposite sides of the crankshaft.
In an arrangement described in Patent Publication 1 below, in order to eliminate a roll moment due to secondary vibration of an engine, a pair of balancer shafts arranged on opposite sides of a crankshaft are staggered in a cylinder axis direction, and the phases of balancer weights provided on these balancer shafts are arranged symmetrically relative to the cylinder axis.
Patent Publication 1: Japanese Utility Model Registration Application Laid-open No. 56-118908
Furthermore, a multi-link engine in which a lower link is pivotably supported on a crankpin of a crankshaft, this lower link is connected to a piston via an upper link, the lower link is connected via a control link to a control shaft supported in an engine block, and the compression ratio is changed by changing the position of one end of the control link by rotating the control shaft by means of an actuator is known from Patent Publications 2 and 3 below.Patent Publication 2: Japanese Patent Application Laid-open No. 2002-188455Patent Publication 3: Japanese Patent Application Laid-open No. 2002-174131Moreover, a variable compression ratio engine that includes a first link connected to a piston, a second link providing a connection between the first link and a crankshaft, and a third link having one end connected to the second link and the other end connected to an engine main body via an eccentric shaft has been proposed in, for example, Patent Publication 4. Furthermore, a variable compression ratio engine that includes a first link connected to a piston, a second link providing a connection between the first link and a crankshaft, and a third link having one end connected to the first link and the other end connected to an engine main body via an eccentric shaft has been proposed in, for example, Patent Publication 5.
Moreover, a variable stroke characteristic engine in which a plurality of links provide a connection between a piston and a crankshaft and the piston stroke is changed by moving an end of one link that is connected to an engine main body has been proposed in, for example, Patent Publications 4 and 5, etc.
Patent Publication 4: Japanese Patent Application Laid-open No. 9-228858
Patent Publication 5: Japanese Patent Application Laid-open No. 2004-150353
On the other hand, an excitation force due to the movement of a piston acts on a reciprocating engine, and since it is difficult to reduce this vibration by means of the cylinder order or a counter weight provided integrally with a crankshaft, an arrangement in which in the multi-link reciprocating engine an attempt is made to reduce the vibration by optimizing the link length or the link position (link geometry) has been proposed in Patent Publication 6.
Furthermore, an excitation force containing primary and secondary vibration components due to the movement of a piston and a connecting rod acts on a reciprocating engine, and since it is difficult to reduce secondary rotational vibration by means of the cylinder order or a counter weight provided integrally with a crankshaft, an arrangement in which in the multi-link reciprocating engine an attempt is made to reduce the vibration by optimizing the link length or the link position (link geometry) has been proposed in Patent Publication 6.
Patent Publication 6: Japanese Patent Application Laid-open No. 2001-227367